The drilling of wells and, in particular, hydrocarbon wells can involve complications that make the process time consuming and expensive. In recognition of these complications and expenses, added emphasis has been placed on increasing efficiencies associated with well completion and with maintenance over the life of the well. Over the years, ever increasing well depths and sophisticated well architectures have made the need to obtain reductions in time and effort spent in completions and maintenance operations even greater.
Perforating and fracturing applications in a cased well, generally during well completion, constitute areas where significant amounts of time and effort are spent. This is particularly true in wells that have increased depth and sophisticated architecture. These applications can involve the positioning of a bridge plug downhole of a well section that is to be perforated and to be fractured. Positioning of the bridge plug may be aided by pumping a driving fluid through the well. Some bridge plugs can be bull-nosed.
A conventional bridge plug can be run down a well on a pipe or on a wire. When run on wire, the bridge plug can be dropped down by gravity through vertical shafts and driven by fluid in horizontal sections. When run on a pipe, the plug can be pushed from surface. Once the bridge plug reaches the desired depth/position, an electrical charge is sent down the pipe and/or wire to cause an explosion. The explosion causes a piston to compress the plug, so that slips extending therefrom, frictionally engage the surface of casing that defines the well. Next, a packer can seal the plug. Optionally, a ball is dropped down through the pipe or through the well to seal everything in pressure isolation.
Once in place, equipment at the oilfield surface may communicate with the plug assembly over conventional wireline to direct the setting of the plug. Once anchored and sealed, a perforation application may take place above the bridge plug so as to provide perforations through the casing in the well section. Similarly, a fracturing application directing fracture fluid through the casing perforations and into the adjacent formation may follow. This process may be repeated, generally starting from the terminal end of the well and moving uphole section by section, until the casing and formation have been configured and treated as desired.
The presence of the set bridge plug in below the well section as indicated above keeps the high pressure perforating and fracturing applications from affecting well sections below the plug. Conventional bridge plugs can be made from inexpensive cast iron, composite materials, or fully-dissolvable materials. Cast iron plugs have a high “drill-out” cost when such plugs must be removed. Composite bridge plugs have higher initial costs and lower drill-out costs. Fully-dissolvable plugs are more expensive, but have lower drill-out costs when such plugs are removed through “clean-out” operations. As a result, there is a need for an improved bridge plug.